The present invention relates to a derivative of 4,5-dihydro-1H-1,2,4-triazole-3-carboxamide utilized as an active ingredient of a herbicide, an intermediate for producing the derivative and a herbicidal composition containing the derivative as an active ingredient.
Rice plant, wheat and corn are the important crop plants, and the use of a herbicide is indispensable for protecting these crop plants from the damage by weeds and for yielding a good harvest of crops.
Hitherto, there have been few reports on the derivatives of 4,5-dihydro-1H-1,2,4-triazole-3-carboxamide, and only a few compounds have been disclosed in Japanese Patent Applications Laying-Open (KOKAI) No. 61-171475(1986) and No. 61-210075(1986) such as those represented by the formula (I'): ##STR2## wherein X represents a hydrogen atom, a 3-methyl group or a 4-chlorine atom, X.sup.1 represents a hydrogen atom and X.sup.2 represents a hydrogen atom, a 4-chlorine atom, a 4-hydroxy group, a 2-hydroxy group, a 2-carboxyl group, a 3-methyl group or a 3-hydroxy group.
Although in Japanese Patent Application Laying-Open (KOKAI) No. 61-210075 (1986), it is described that the compound represented by the formula (I') has a herbicidal activity, the herbicidal effect of the compound is not satisfactory and also the selectivity of the compound cannot be said to be excellent, therefore, the development of a compound which shows an excellent selective herbicidal activity only to weeds without damaging the useful crop plants such as rice plant, wheat, corn, etc. has been strongly demanded.
As a result of the present inventors' studies for developing a compound which shows an excellent herbicidal activity without damaging the useful crop plants such as rice plant, wheat, corn, etc., it has been found out by the present inventors that a derivative of 4,5-dihydro-1H-1,2,4-triazole-3-carboxamide represented by the formula (I): ##STR3## wherein R.sup.1 represents a hydrogen atom, a halogen atom, an alkyl group of 1 to 3 carbon atoms or an alkoxy group of 1 to 3 carbon atoms, R.sup.2 represents a hydrogen atom or a halogen atom and R represents a straight-chain alkyl group of 1 to 8 carbon atoms, a branched-chain alkyl group of 3 to 8 carbon atoms, a cycloalkyl group of 3 to 8 carbon atoms, a (cycloalkyl)alkyl group of 4 to 8 carbon atoms, an alkenyl group of 3 to 8 carbon atoms, an alkynyl group of 3 to 8 carbon atoms, an alkoxyalkyl group of 3 to 8 carbon atoms, a phenyl group, an aralkyl group of 7 to 9 carbon atoms, a phenyl group substituted by halogen atom(s) or an alkyl group of 2 to 8 carbon atoms which is substituted by fluorine atom(s), has an excellent selective herbicidal activity and further that a derivative of methyl chlorophenylhydrazonoacetate represented by the formula (II): ##STR4## wherein R has the same meaning as above and a phenylhydrazone derivative of oxamide represented by the formula (III): ##STR5## wherein R has the same meaning as above, are useful as the intermediate for producing the derivative of 4,5-dihydro-1H-1,2,4-triazole-3-carboxamide, and on the basis of the findings, the present inventors have accomplished the present invention.